This invention relates to a heat-sensitive record material and particularly to a heat-sensitive record material which is superior in record sensitivity and can develop color images having a good quality.
There has been well known heat-sensitive record materials utilizing the colorforming reaction between a basic colorless chromogenic material and an electron accepting acidic color developing material, in which color images are produced by heating to contact with each other of the basic colorless chromogenic material and the electron accepting acidic color developing material. The heat-sensitive recording materials are relatively cheep and the recording machine is compact and easy to maintain. Accordingly, they have been used in various fields as well as a record medium in facsimiles, computers and the like.
The recording speed becomes higher and resultantly requirements for the heat-sensitive record materials superior in dynamic record sensitivity have been increased. Further, the applied fields becomes wider. It is required for the heat-sensitive record material to develop color images having a good quality in any color density.
In order to satisfy the requirements, it has been proposed to form a middle layer between the base sheet and the recording layer. However, the required conditions such as coating method, coating composition and concentration of it have not yet been satisfactly studied, and a practical useful middle layer has not been obtained.
The object of the invention is to provide a heat-sensitive record materials having a very effective middle layer between the base sheet and the recording layer, which can develop color images superior in color density and having a good quality.